It is indispensable to use a random number for high level scientific calculation, a game machine, encryption processing or the like, and in recent years, the demand for a high performance generator of a natural random number (true random number) with uniformity (a difference in occurrence ratio is not produced according to a random number) and without regularity of random number occurrence, before-and-after correlativity, periodicity and the like, or a probability generator has been escalating.
Then, as the above natural random number/probability generator, one using a random pulse obtained by use of, for example, extremely weak radiation, thermal noise of a resistor or a diode, fluctuation of a crystal oscillator, or the like is well known.
However, in the random number/probability generating circuit using the random pulse by the above natural phenomenon, since analog components, such as a generating source of the random pulse, an amplifier of a signal, waveform shaping, and an optimizing circuit of uniformity, are much included, the circuit scale becomes large and complicated, and accordingly, it is difficult to mount these as an integrated logic LSI, and it also becomes disadvantageous for application to a microminiature and thin high-tech equipment, such as an IC card, the demand of which is expected to be increased in future. Besides, since the formation as an LSI is difficult, the productivity is poor and the cost becomes high.
Especially, since one using the thermal noise is apt to be influenced by an external noise, power supply fluctuation, temperature or the like, there is a defect that it is lacking in operation stability. Besides, with respect to one using radiation, since there is a fear that the radiation influences the environment or the like even though it is extremely weak, the amount of usable radiation has a limit, and it has been difficult to cope with such a use that a lot of random numbers are generated in a short time.